The present invention relates to methods for making duplicate parts during lathe turning operations and, more particularly, for a system attachable to a multipurpose woodworking tool for holding a pattern and cutting a duplicate part in a lathe turning operation.
A lathe typically includes a headstock having a motor-driven quill spindle and drive center for engaging the end of a workpiece, a tailstock having a center for engaging an opposite end of a workpiece, a tool rest for supporting a tool, and a frame for supporting the headstock, tailstock, and tool rest. This type of lathe, in which the workpiece is held between centers, is used to perform "spindle turning" to make such items as legs for tables, chairs, and beds. Lathes are also used to turn bowls, goblets, and the like in a procedure called "face plate turning". In this procedure, the pointed centers are removed from the headstock and tailstock, and the headstock drive center is replaced with a disc-shaped face plate which is screwed to a scrap block that, in turn, is removably attached to the workpiece to be turned.
It is frequently necessary to turn a large number of identically-shaped pieces on a lathe, and such an operation is performed most efficiently by the use of a lathe duplicator. A lathe duplicating system is shown in the Hochstatter et al. U.S. Pat. No. 4,256,155, and includes a frame having a motorized headstock, displaceable tailstock, and a horizontal table extending between the headstock and tailstock. A cutting tool is mounted on a tool holder that is freely slidable on the table. The tool holder also includes a follower which engages the contours of a model supported by brackets mounted on the table. The brackets include a clamp which is adapted to engage a flat template, and may be modified to receive bracket extensions having spindles for holding a three dimensional model to be duplicated.
In operation, the pattern to be duplicated--in the form of a flat template or a three-dimensional model --is mounted on the brackets, and the tool holder is moved along the support surface so that the follower traces the contour of the pattern. At the same time, the cutting tool engages the rotating workpiece and removes material to form a contour corresponding to that of the pattern. Since the tool holder is freely movable along the supporting surface, such lathe duplicating systems are capable of duplicating intricate patterns which may include negative or reverse curvatures. Such systems are known as "free foot" duplicators.
Another example of a free foot duplicator is shown in the Messick U.S. Pat. No. 3,768,527. With that system, the flat table top is slidably positionable beneath the headstock and tailstock of the associated lathe, and includes a slot which is shaped to receive the downwardly-extending lip of a template having the pattern to be duplicated. Models are held between the adjustable spindles of brackets attached to opposite ends of the table top. The tool holder includes a low friction base for sliding on the table top, a follower which is adjustably attachable to the base, a second follower which is adjustably positionable along an upright post extending from the base, and a cutting tool support which is adjustably attached to the top of the post.
In both of the aforementioned devices, the template or model to be duplicated is positioned below the rotational axis of the headstock and therefore below the spinning workpiece. The disadvantage of this arrangement is that the maximum diameter of the workpiece is somewhat limited since a portion of the space between the rotational axis and the support surface for the tool holder is occupied by the template or model.
Another disadvantage with the aforementioned systems is that the templates must be specially modified in order to be attached to the support brackets. With the system of Hochstatter et al., the template must have parallel slots formed in its ends, and with the system of Messick, the template must have holes formed in its ends. Both, therefore, require additional fabricating steps to be performed on a flat template. In addition, neither of the aforementioned lathe duplicating systems are readily mountable on a multipurpose woodworking machine, such as that shown in the Edgemond, Jr., et al. U.S. Pat. No. 2,927,612, which can be set up to function as a lathe.
A disadvantage with free foot systems currently in use is that the tool holders are designed to hold a single, elongate cutting tool having a cutting edge of a predetermined shape, such as round or pointed. Consequently, in order to change the shape of the cutting edge, the entire cutting tool must be removed and replaced with one having the desired edge. Another disadvantage with tool holders of free foot systems is that they lack means for quickly and accurately aligning the cutting tool tip with the follower tip, or offsetting the cutting tool tip a predetermined amount from the follower tip.
Accordingly, there is a need for a lathe duplicating system of the free foot type in which the space between the table top and the rotational axis of the workpiece is unobstructed so that large diameter workpieces may be turned. There is also a need for a lathe duplicating system which is readily convertible to hold either a flat template or a three-dimensional model, and which accepts templates for face plate turning as well as spindle turning without requiring additional, modifying operations. Furthermore, there is a need for a lathe duplicating system which is readily attachable to a multipurpose woodworking tool. There is also a need for a tool support which provides for accurate and rapid alignment of the cutting tool and follower, and which does not require a plurality of separate cutting tools to provide a variety of cutting edge shapes.